Oh dear. Back to school!

Re: Oh dear. Back to school!

Postby TenMetrePeter » Sun Oct 22, 2017 7:53 pm

Cannot defy gravity even for a nanosecond. Thats why an angled flight becomes a parabola as soon as it leaves the barrel. Pellet will never be above the centre line of the barrel.

Furthermore you could hit the same target (ignoring air effects) by tilting the barrel above 45° by the same amount as the barrel was below 45°. Field gun vs howitzer.

Barrel 45° to horizontal will give maximum range. Same as javelin etc.
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Re: Oh dear. Back to school!

Postby Timmytree » Sun Oct 22, 2017 8:13 pm

TenMetrePeter wrote:Cannot defy gravity even for a nanosecond. Thats why an angled flight becomes a parabola as soon as it leaves the barrel. Pellet will never be above the centre line of the barrel.

Furthermore you could hit the same target (ignoring air effects) by tilting the barrel above 45° by the same amount as the barrel was below 45°. Field gun vs howitzer.

Barrel 45° to horizontal will give maximum range. Same as javelin etc.


So my 11+ education wasn't wasted? No further education, no university but I'm right?
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Re: Oh dear. Back to school!

Postby TenMetrePeter » Sun Oct 22, 2017 8:37 pm

Yes you're right. The diagram doesnt clearly show 2 zero points but there are 2 with a high scope.

With my 10m rifle the 10m target is before the highest point of the parabola so if I then shoot closer at 6 yards the pellet hits an inch low and has to be wound up 80 clicks.
With my pistol with low sightline the 6 yard and 10m targets correspond to the 2 zero points (by coincidence) and no adjustment is needed.

p.s. I did go to university and all you missed was 3 years of agony and 20 years of bad anxiety dreams. I wouldnt pay 40 grand for it now.
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Re: Oh dear. Back to school!

Postby Smudgerii » Mon Oct 23, 2017 10:18 am

An arc yes, due to sight position as stated. Does the pellet climb? No it does not. Does it immediately fall? No, not immediately as gravity has to ovecome the velocity if the projectile. The rate of fall is based on velocity, projectile weight and even your location on earth ( thats why the lauch space rickets in certain locations )

But hey go with what you like that way it’s easier to come on here and slag off a guy from another forum that you disagree with....

Ps. If you can’t defy gravity what are all those aeroplanes doing?

Pps. Two ‘zero points’ with every sighting set up high or low mounted, thats it if you have zeroed it... just physics
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Re: Oh dear. Back to school!

Postby wastrel » Mon Oct 23, 2017 6:47 pm

well I`m lost, does the pellet rise (in it`s arc) or not? I thought it did!
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Re: Oh dear. Back to school!

Postby Timmytree » Mon Oct 23, 2017 6:52 pm

wastrel wrote:well I`m lost, does the pellet rise (in it`s arc) or not? I thought it did!


No, fire a pellet with the barrel parallel to the ground and the pellet starts dropping the instant it leaves the barrel. It's only the scope pointing downwards that gives the illusion of a rising pellet. It's physically impossible for any projectile to rise above the line of the bore or barrel.
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Re: Oh dear. Back to school!

Postby TenMetrePeter » Mon Oct 23, 2017 6:54 pm

Smudgerii wrote:An arc yes, due to sight position as stated. Does the pellet climb? No it does not. Does it immediately fall? No, not immediately as gravity has to ovecome the velocity if the projectile. The rate of fall is based on velocity, projectile weight and even your location on earth ( thats why the lauch space rickets in certain locations )

But hey go with what you like that way it’s easier to come on here and slag off a guy from another forum that you disagree with....

Ps. If you can’t defy gravity what are all those aeroplanes doing?

Pps. Two ‘zero points’ with every sighting set up high or low mounted, thats it if you have zeroed it... just physics


Smudgerii, just because it it going upwards does not mean it isnt accelerating downwards at the gravitational rate of 32 ft/sec/sec.
You need to understand the difference between velocity and acceleration. Believe me even though it is moving up it is accelerating down.
One advantage of studying applied maths at higher level.

Aeroplanes do not "defy" gravity as it is acting on them all the time They have a shaped wing where air moves faster above the wing than below and the difference in pressure balances out the force of gravity.
Even when spinning a diabolo does not have differential surfaces or pressures like a wing. It accelerates towards the ground at 32 ft/sec/sec even though it is travelling upwards for the first part of its travel.
The spin applies a stabilisation due to gyroscopic effect which can keep the pellet facing forwards but cannot reduce the rate of gravitational acceleration downwards.

Gravitational acceleration towards earth depends on altitude but not on velocity or weight (more correctly Mass because weight also changes with altitude) of the object. Heavier pellets drop more only because they take longer to get to the target and vertical velocity accelerates downwards for longer.

Hope this helps :lol:

ps Wastrel yes pellet does go up because the barrel points up but never above the centreline of the barrel, like Timmytree said.
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Re: Oh dear. Back to school!

Postby robertt » Sat Oct 28, 2017 10:08 am

Had the same heated discussion with an alledged ex army smallarms instructor who had obviously skipped a big paragraph in the tradjectory chapter.

An ex squaddy backed him up saying ' yes , I've watched tracers go up before they come down.'

They the would not accept the fact that a bullet drops when leaving the barrel and the rise and fall of the is an illusion created by the line of sight intersecting the tradjectory at 2 points.

There's a good article if you search Ballistics for Dummies but I couldn't attach link.
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Re: Oh dear. Back to school!

Postby eboswan » Sat Oct 28, 2017 10:41 am

IS MY SIGNATURE BIGGER THAN RAYS. Cz 452 american .22+sak mod
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Re: Oh dear. Back to school!

Postby robertt » Sat Oct 28, 2017 11:07 am

Thats the one. Thanks :)
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